Tunable 3D novel metamaterial unit cell enabling Super-Chiral, Semi-Achiral, and zero Poisson's ratio structures

摘要

Realizing customizable deformation in 3D metamaterials remains a key challenge, especially controlling the coupling between axial strain and twist. Such tunable responses are increasingly needed in soft robotics, adaptive structures, and multifunctional devices with properties beyond conventional materials. This work presents a novel 3D chiral metamaterial unit cell with unique deformation mechanisms under compression. Finite Element simulations (COMSOL Multiphysics 6.2) were validated via experiments on 3D-printed samples. The unit cell shows two behaviors governed by six geometric parameters: (1) a Semi-Achiral mechanism involving lateral compression and expansion without twisting, and (2) a Super-Chiral mechanism with compression-twist coupling and a twist-to-strain ratio of 3.7. Multi-cell structures were analyzed for connectivity and configurations. By adjusting network arrangements, three tunable behaviors were achieved: Super-Chiral, Semi-Achiral, and zero Poisson's ratio – the latter by balancing clockwise and counterclockwise units. Layout strongly affected performance, with up to 150% variation in effective elastic modulus across 32 configurations. The twist-to-strain ratio increased with more unit cells longitudinally and decreased with more cells transversely. By altering the geometry of individual unit cells or the overall dimensions of the metamaterial, this structure has the potential to offer precise control over mechanical responses, enabling features tailored to specific application requirements. • A new three-dimensional metamaterial design was developed to enable tunable mechanical behavior by adjusting geometric parameters. • A single unit cell configuration exhibited either compression-induced - twisting, with a twist-to-strain ratio of 3.7 , or twist-negligible compressive deformation, with a ratio close to zero. • An achiral response with nearly zero lateral strain under compression achieved by adjusting the orientation of unit cells. • In the achiral, zero Poisson's ratio configuration, the effective elastic modulus varied by up to 150% based on the unit cell layout.